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Biomedical subjects

Robert O Bonow

Publications and source records attributed to Robert O Bonow.

At least 19 recordsLinked to original sources
PubMed2004

Left ventricular function during and after right ventricular pacing.

OBJECTIVES: The aim of this research was to evaluate right ventricular pacing effects on left ventricular function. BACKGROUND: Right ventricular pacing alters the ventricular activation sequence and reduces left ventricular ejection fraction (EF). It is unclear whether the observed reduction in EF can be completely attributed to the alteration in activation sequence. METHODS: Twelve subjects (eight women), mean age 68 +/- 12 years, with transvenous dual-chamber pacemakers, normal left ventricular function, and intact atrioventricular (AV) conduction were studied with serial-gated blood pool studies. Left ventricular EF was measured at a fixed rate after at least 1 week of atrial pacing only (baseline), during short-term (2 h) and mid-term (1 week) AV sequential pacing with a short AV delay, and after short- and mid-term AV pacing. RESULTS: Baseline EF was 66.5 +/- 4.5%. Short-term AV pacing resulted in a decrease in EF to 60.3 +/- 5.2% (p < 0.0002). After one week of AV pacing, there was a further decline in EF to 52.9 +/- 8.3% (p < 0.0001). After cessation of mid-term pacing, EF was 57.3 +/- 5.9% (p < 0.0001 vs. baseline). A total of 2, 5, 8, and 24 h later, EF remained depressed (59% to 60%, p < 0.007). At 32 h, EF was 62.9 +/- 7.6% (p < 0.11 compared with baseline). CONCLUSIONS: The abnormal activation sequence resulting from right ventricular pacing accounts for only part of the reduction in EF as mid-term pacing is associated with a lower EF than short-term pacing, and EF remains depressed after cessation of AV pacing. Changes in ventricular function induced by right ventricular pacing may account for some of its associated adverse effects.

Aged↗
PubMed2004

Relation between contractile reserve and improvement in left ventricular function with beta-blocker therapy in patients with heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

Beta blockers improve left ventricular (LV) ejection fraction but patient responses are heterogenous. We investigated the role of contractile reserve (CR) in predicting beta-blocker response in ischemic and nonischemic cardiomyopathy. Resting and low-dose dobutamine echocardiograms were recorded in 32 patients with heart failure (LV ejection fraction <or=35%), 18 with ischemic cardiomyopathy (IC), and 14 with idiopathic dilated cardiomyopathy (IDC). A segment was defined as CR positive (CR+) or negative (CR-) based on response to dobutamine. Patients were then classified as CR+ or CR- based on number of improved segments (IC group) or ejection fraction improvement (IDC group) in response to dobutamine. During follow-up (2, 6, and 14 months after beta-blocker initiation), response was measured by the percent of segments showing improved contractility from baseline, ejection fraction, and wall motion score index. In the IC group, the percent of improved segments was greater at 2 and 6 months in CR+ versus CR- (70% vs 15% and 39% vs 17%, p <0.05), whereas it was greater at all periods in the patients with IDC (36% vs 9% at 2 months, 50% vs 19% at 6 months, and 63% vs 42% at 14 months, p <0.05). Findings for ejection fraction and wall motion score index were similar. Therefore, time course and magnitude of improvement in LV function in patients with heart failure receiving beta blockers are related to CR status. CR predicts a greater early response in IC, whereas it predicts a greater response at all time periods in IDC. However, even patients without CR showed improvement in LV function at 14 months.

Adrenergic beta-Antagonists↗
PubMed2004

The diabetes epidemic: a national and global crisis.

Diabetes mellitus is a serious problem that will soon reach epidemic proportions in the United States and throughout the world. The incidence of this condition will skyrocket in the next quarter century as demographic changes increase the size of highly susceptible populations (e.g., the elderly and Hispanic communities) and sociocultural developments create a more sedentary populace as well as expose people in developing nations to new risk factors for this disease. Along with substantial direct morbidity and mortality, diabetes is independently associated with the incidence and severity of a variety of cardiovascular illnesses. Individuals with diabetes are substantially more likely than their nondiabetic counterparts to suffer stroke, myocardial infarction, or heart failure, with a worse prognosis following any of these conditions. Many factors may be relevant to this association, but recent studies have elucidated a major role for the metabolic syndrome, which has been shown to be predictive of both diabetes and cardiovascular disease. Consequently, early intervention to control blood glucose levels and other risk factors may mitigate the severity of these conditions, possibly even before the disease begins.

Cardiovascular Diseases↗
PubMed2004

New insights into diastolic heart failure: role of diabetes mellitus.

Heart failure affects nearly 5 million people in the United States and is a major contributor to mortality, hospitalization, and medical costs. Approximately 40% of patients with heart failure have preserved left ventricular systolic function, thus exhibiting diastolic heart failure. More common in women and the elderly, this condition is associated with hypertension, coronary artery disease, and/or atrial fibrillation. With the exception of the Digitalis Investigation Group (DIG) and the Candesartin in Heart Failure: Assessment of Reduction in Mortality and Morbidity (CHARM)-Preserved trials, no completed large randomized clinical trial has addressed the management of such patients. Symptomatic treatment involves administration of diuretics and nitrates, but long-term management with angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, aldosterone antagonists, beta-blockers, and calcium channel blockers targets the underlying disorders. Recent studies found that diabetes mellitus produces functional, biochemical, and morphologic myocardial abnormalities independent of coronary atherosclerosis and hypertension. These abnormalities may result in impaired left ventricular diastolic function, contributing importantly to heart failure with normal systolic function. Although tight glycemic control decreases the risk of heart failure in patients with diabetes, the effects of different diabetic treatment regimens on heart failure with normal systolic function are unknown and remain subject to future investigation.

Aging↗
PubMed2004

Closing statement.

Explore the source record for details and available documents.

Cardiovascular Diseases↗
PubMed2004

Mitral regurgitation in chronic heart failure: more questions than answers?

The presence, implications, and approach to mitral valvular disease in the setting of a cardiomyopathy has recently become a focal issue for discussion. Although recent evidence suggests that mitral regurgitation confers a poor prognosis in heart failure, the true prevalence of mitral regurgitation as well as its pathogenic contribution to prognosis in heart failure remains uncertain. Whereas angiotensin-converting enzyme inhibitors have not been demonstrated to favorably alter mitral regurgitation, treatment with b-blockers or cardiac resynchronization therapy has been shown to induce regression of ventricular dilation, with consequent decrease in mitral regurgitation. Surgical valve reconstruction by undersized ring annuloplasty appears promising, but optimal results require skilled surgical expertise. Even in highly experienced hands, intermediate outcomes appear to be inferior to those of cardiac transplantation. Percutaneous mitral valve repair remains an investigational procedure that warrants further clinical research.

Heart Failure↗